a) (x la a doua+2x+1)-(y la a doua-4y+4)=(x+1)²-(y-2)²=(x+1-y+2)(x+1+y-2)=(x-y+3)(x+y-1)
b)9a la doua-(x la a doua -6x+9) = 9a²-(x-3)²=(3a-x+3)(3a+x-3)
c)x la a doua+4x+4-16y la a doua=(x+2)²-16y²=(x+2-4y)(x+2+4y)
d)x la a doua+10x+25-9y la a doua=(x+5)²-9y²=(x+5-3y)(x+5+3y)
